The present invention relates to a transfer apparatus for transferring flat substrates, e.g., semiconductor wafers, and a container for storing them, and a treatment system using the transfer apparatus.
In the manufacture of semiconductor devices, a treatment system such as a vertical heat treatment system is used to perform various types of treatments, e.g., oxidation, diffusion, CVD, and the like, for semiconductor wafers as target substrates. In this treatment system, a cassette (also called a carrier) as a transport container storing a plurality of wafers is loaded/unloaded by a transport robot or an operator through an in/out section. A cassette storing new wafers is arranged on a shelf in the system, and the wafers are mounted from the cassette on the shelf to a boat. The boat on which the wafers are mounted is charged in a heat treatment furnace, and the wafers are subjected to a predetermined treatment. When the predetermined heat treatment is ended, the boat is unloaded from the heat treatment furnace, and the treated wafers are returned from the boat to the cassette in the order opposite to that described above.
A transfer apparatus in which a cassette transfer member is attached to the drive system of a wafer transfer member in such a treatment system is known (Jpn. Pat. Appln. KOKAI Publication No. 3-48439). This transfer apparatus has a vertically movable and rotatable base, and a cassette transfer member attached to the base, in addition to the wafer transfer member. The cassette transfer member is disposed back to back with the wafer transfer member, and is advanced and retreated by an air cylinder in a direction opposite to the wafer transfer member. This reduces the space occupied by the transfer mechanism and down-sizes the treatment system.
In this transfer apparatus, the radius of turn during cassette transfer becomes large because of the usage of the air cylinder and the arrangement of the cassette transfer member. A certain degree of extra space be given around the transfer apparatus, thus limiting any reduction in space in the horizontal direction. This problem becomes conspicuous particularly as the diameter of the wafer increases and accordingly the size of the cassette increases.